A flexible multichannel wearable sensor for real-time monitoring of exercise-induced sweat composition

To address low sensitivity, severe environmental interference, single-analyte detection, and traditional rigid substrates' inability to adapt to dynamic skin deformation in surface metabolite detection, polyethylene terephthalate (PET) was selected as the flexible substrate. A multi-channel flexible wearable biosensor with mechanical adaptability and multi-parameter detection capability was constructed via screen-printing, integrating four independent working electrodes sharing one reference and counter electrode, enabling real-time quantification of K⁺, NH₄⁺, lactic acid (LA), and ascorbic acid (AA) in human sweat. Experimental results demonstrate the sensor's excellent detection performance. For K⁺, the sensitivity is 89.9 mV decade^-1 within the concentration range of 0.5-12 mM; for NH₄⁺, it is 55.9 mV decade^-1 over 0.2-4 mM; for LA, the sensitivity reaches 86 nA mM^-1 across 5-40 mM; and for AA, the sensitivities are 2.62 μA μM^-1 (2-10 μM) and 1.17 μA μM^-1 (10-60 μM), respectively. Notably, all detection limits and linear ranges align with human sweat's physiological concentration range. Moreover, the sensor demonstrates excellent selectivity toward target analytes, long-term stability, and good reproducibility. Flexibility tests show 0°-120° bending and 100 cycles have negligible effects. Moreover, placing the sensor on the subjects' forehead enabled non-invasive continuous monitoring of sweat K⁺, NH₄⁺, LA, and AA dynamics during 30-min exercise. This work verifies the sensor's potential in sports health monitoring and personalized athletic performance tracking, while advancing wearable sensing technology toward higher precision and integration.